// Copyright © 2021 rsiddharth <s@ricketyspace.net>
// SPDX-License-Identifier: ISC
package lib
// MD4 implementation.
// Reference https://datatracker.ietf.org/doc/html/rfc1320
type Md4 struct {
hvs []uint32
Msg []byte
MsgLen int
}
// Initial hash value.
var md4IHashValues []uint32 = []uint32{
0x67452301,
0xefcdab89,
0x98badcfe,
0x10325476,
}
func md4F(x, y, z uint32) uint32 {
return (x & y) | (^x & z)
}
func md4G(x, y, z uint32) uint32 {
return (x & y) | (x & z) | (y & z)
}
func md4H(x, y, z uint32) uint32 {
return x ^ y ^ z
}
func md4RoundOneFunc(a, b, c, d, x uint32, s uint) uint32 {
a = shaAdd(a, md4F(b, c, d), x)
a = shaRotl(a, s)
return a
}
func md4RoundTwoFunc(a, b, c, d, x uint32, s uint) uint32 {
a = shaAdd(a, md4G(b, c, d), x, 0x5A827999)
a = shaRotl(a, s)
return a
}
func md4RoundThreeFunc(a, b, c, d, x uint32, s uint) uint32 {
a = shaAdd(a, md4H(b, c, d), x, 0x6ED9EBA1)
a = shaRotl(a, s)
return a
}
func md4Padding(l int) []byte {
l = l * 8 // msg size in bits
// Reckon value of `k`
k := 0
for ((l + 1 + k) % 512) != 448 {
k += 1
}
// Initialize padding bytes
pbs := make([]byte, 0)
// Add bit `1` as byte block.
pbs = append(pbs, 0x80)
f := 7 // unclaimed bits in last byte of `pbs`
// Add `k` bit `0`s
for i := 0; i < k; i++ {
if f == 0 {
pbs = append(pbs, 0x0)
f = 8
}
f = f - 1
}
// Add `l` in a 64 bit block in `pbs`
l64 := uint64(l)
b64 := make([]byte, 8) // last 64-bits
for i := 0; i <= 7; i++ {
// Get 8 last bits.
b64[i] = byte(l64 & 0xFF)
// Get rid of the last 8 bits.
l64 = l64 >> 8
}
pbs = append(pbs, b64...)
return pbs
}
func md4MessageBlocks(pm []byte) [][]uint32 {
// Break into 512-bit blocks
bs := BreakIntoBlocks(pm, 64)
mbs := make([][]uint32, 0) // Message blocks.
for i := 0; i < len(bs); i++ {
ws := make([]uint32, 0) // 32-bit words.
// Break 512-bit (64 bytes) into 32-bit words.
for j := 0; j < 64; j = j + 4 {
// Pack 4 bytes into a 32-bit word.
w := (uint32(bs[i][j]) |
uint32(bs[i][j+1])<<8 |
uint32(bs[i][j+2])<<16 |
uint32(bs[i][j+3])<<24)
ws = append(ws, w)
}
mbs = append(mbs, ws)
}
return mbs
}
func (md *Md4) Init(hvs []uint32) {
// Set Initial Hash Values.
h := make([]uint32, 4)
if len(hvs) == 4 {
copy(h, hvs)
md.hvs = h
} else {
copy(h, md4IHashValues)
md.hvs = h
}
}
func (md *Md4) Message(m []byte) {
md.Msg = m
md.MsgLen = len(m)
}
// MD4 - Pad message such that its length is a multiple of 512.
func (md *Md4) Pad() []byte {
// Initialize padded message
pm := make([]byte, len(md.Msg))
copy(pm, md.Msg)
// Add padding.
pm = append(pm, md4Padding(md.MsgLen)...)
return pm
}
func (md *Md4) Hash() []byte {
// Pad message.
pm := md.Pad()
// Break into message blocks.
mbs := md4MessageBlocks(pm)
// Initialize hash values.
h := make([]uint32, 4)
copy(h, md.hvs) // Initial hash values.
// Process each message block.
for _, mb := range mbs {
// Initialize working variables.
a := h[0]
b := h[1]
c := h[2]
d := h[3]
// Round 1.
a = md4RoundOneFunc(a, b, c, d, mb[0], 3)
d = md4RoundOneFunc(d, a, b, c, mb[1], 7)
c = md4RoundOneFunc(c, d, a, b, mb[2], 11)
b = md4RoundOneFunc(b, c, d, a, mb[3], 19)
a = md4RoundOneFunc(a, b, c, d, mb[4], 3)
d = md4RoundOneFunc(d, a, b, c, mb[5], 7)
c = md4RoundOneFunc(c, d, a, b, mb[6], 11)
b = md4RoundOneFunc(b, c, d, a, mb[7], 19)
a = md4RoundOneFunc(a, b, c, d, mb[8], 3)
d = md4RoundOneFunc(d, a, b, c, mb[9], 7)
c = md4RoundOneFunc(c, d, a, b, mb[10], 11)
b = md4RoundOneFunc(b, c, d, a, mb[11], 19)
a = md4RoundOneFunc(a, b, c, d, mb[12], 3)
d = md4RoundOneFunc(d, a, b, c, mb[13], 7)
c = md4RoundOneFunc(c, d, a, b, mb[14], 11)
b = md4RoundOneFunc(b, c, d, a, mb[15], 19)
// Round 2
a = md4RoundTwoFunc(a, b, c, d, mb[0], 3)
d = md4RoundTwoFunc(d, a, b, c, mb[4], 5)
c = md4RoundTwoFunc(c, d, a, b, mb[8], 9)
b = md4RoundTwoFunc(b, c, d, a, mb[12], 13)
a = md4RoundTwoFunc(a, b, c, d, mb[1], 3)
d = md4RoundTwoFunc(d, a, b, c, mb[5], 5)
c = md4RoundTwoFunc(c, d, a, b, mb[9], 9)
b = md4RoundTwoFunc(b, c, d, a, mb[13], 13)
a = md4RoundTwoFunc(a, b, c, d, mb[2], 3)
d = md4RoundTwoFunc(d, a, b, c, mb[6], 5)
c = md4RoundTwoFunc(c, d, a, b, mb[10], 9)
b = md4RoundTwoFunc(b, c, d, a, mb[14], 13)
a = md4RoundTwoFunc(a, b, c, d, mb[3], 3)
d = md4RoundTwoFunc(d, a, b, c, mb[7], 5)
c = md4RoundTwoFunc(c, d, a, b, mb[11], 9)
b = md4RoundTwoFunc(b, c, d, a, mb[15], 13)
// Round 3
a = md4RoundThreeFunc(a, b, c, d, mb[0], 3)
d = md4RoundThreeFunc(d, a, b, c, mb[8], 9)
c = md4RoundThreeFunc(c, d, a, b, mb[4], 11)
b = md4RoundThreeFunc(b, c, d, a, mb[12], 15)
a = md4RoundThreeFunc(a, b, c, d, mb[2], 3)
d = md4RoundThreeFunc(d, a, b, c, mb[10], 9)
c = md4RoundThreeFunc(c, d, a, b, mb[6], 11)
b = md4RoundThreeFunc(b, c, d, a, mb[14], 15)
a = md4RoundThreeFunc(a, b, c, d, mb[1], 3)
d = md4RoundThreeFunc(d, a, b, c, mb[9], 9)
c = md4RoundThreeFunc(c, d, a, b, mb[5], 11)
b = md4RoundThreeFunc(b, c, d, a, mb[13], 15)
a = md4RoundThreeFunc(a, b, c, d, mb[3], 3)
d = md4RoundThreeFunc(d, a, b, c, mb[11], 9)
c = md4RoundThreeFunc(c, d, a, b, mb[7], 11)
b = md4RoundThreeFunc(b, c, d, a, mb[15], 15)
// Compute intermediate hash values.
h[0] = shaAdd(a, h[0])
h[1] = shaAdd(b, h[1])
h[2] = shaAdd(c, h[2])
h[3] = shaAdd(d, h[3])
}
// Slurp md4 digest from hash values.
d := make([]byte, 0) // md4 digest
for i := 0; i < 4; i++ {
// Break 32-bit hash value into 4 bytes.
hb := make([]byte, 4)
for j := 0; j <= 3; j++ {
// Get last 8 bits.
hb[j] = byte(h[i] & 0xFF)
// Get rid of last 8 bits.
h[i] = h[i] >> 8
}
d = append(d, hb...)
}
return d
}
